The molecular basis of HLA-unrestricted recognition is not known. Peripheral blood leukocytes stimulated with IL-2 can express the ability to recognize and kill a variety of targets in a HLA-unrestricted manner. Two models have been proposed to explain the molecular basis of HLA- unrestricted and TCR-independent recognition. The first model states that activation by IL-2 induces the expression of unique LAK-like receptors that recognize and blind common target structures. However, no purely NK or LAK cell-specific receptor has been characterized; thus this model remains to be confirmed. The alternative model states that HLA- unrestricted cytotoxicity is mediated by multiple monomorphic receptors that recognize different ligands on the target cells. The number of different types of molecules that are implicated in mediating LAK-tumor cell interaction supports the second hypothesis. I have recently shown that a subset of the CD3+LAK cells are stimulated by tumor cells to produce tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). The stimulation of these T cells is not dependent on target cell-expression of HLA antigens. My preliminary data support previously published reports that leukocyte integrins may be important mediators of such HLA-unrestricted recognition. The major objectives of this project are: (1) to determine whether monomorphic integrins and cell adhesion molecules (CAMs) are sufficient to fully mediate the stimulation of CD3+LAK cells to produce TNF-alpha and IFN- gamma, or if other, possibly LAK cell-associated molecules, are necessary for maximum stimulation. To address the possibility that the CD3+LAK cells are heterogeneous with respect with their ability to recognize tumor cells cloned CD3+LAK and will be used in some of these studies. (2) to determine whether the ligands that stimulate the production of TNF-alpha and INF- gamma by CD3+LAK cells, also mediate the ability of cloned CD3+LAK and purified IL-2 activated-NK cells to lyse, can tumor cells. (3)To determine whether normal cells, which are reported to be resistant to LAK cell- mediated lysis, can stimulate LAK cell to produce TNF-alpha and IFN-gamma, and, if so, whether that ability is correlated with the expression of the same stimulatory ligands as those originally identified on tumor cells. The basic research that I am proposing will utilize LAK cells as an experimental model for studying HLA-unrestricted recognition. These studies will allow me to define the molecules that can trigger IL-2 activated T cells to produce TNF-alpha and IFN-gamma. The identify of these stimulatory molecules will provide insights into the roles LAK cells and the released cytokines play in vivo.